This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application PLASMA DRY SCRUBBER filed with the Korean Industrial Property Office on Jun. 27, 2000 and there duly assigned Serial No. 35786/2000.
1. Technical Field
The present invention relates to a dry scrubber and, more particularly, to a plasma dry scrubber for scrubbing the gas exhausted during a semiconductor manufacturing process by means of physical and chemical decomposition actions using plasma.
2. Description of the Prior Art
Semiconductor devices are manufactured via a plurality of processes. Among semiconductor manufacturing processes, especially a diffusion process and an etching process are repeated frequently. After completion of the processes, gas remaining in a process chamber is discharged to the outside via a discharging system. However, among gases used in the semiconductor manufacturing process, such as the diffusion process, etching process or the like, there exist noxious gases, such as CF4, CHF3, C2F6, or the like. On this account, it is required that the gas discharged through the discharging system be subject to an additional cleaning process. For that purpose, dry or wet scrubbers are used at present.
Generally, in accordance with the decomposition process, such as heat decomposition or plasma decomposition, a gas scrubber is used for dry scrubbing. It is known that it is difficult to decompose noxious gases effectively below the allowed concentration by gas scrubbing according to the plasma process. The reason for such a disadvantage is as follows:
The plasma process is divided into an ICP (inductive coupled plasma) process and a CCP (capacitive coupled plasma) process in accordance with the plasma generation configuration. The ICP process has a drawback in that the uniformity of the magnetic field is not maintained due to its constructional characteristic. Also, the capability of gas decomposition is reduced if the diameter of the discharging pipe is increased. Particularly, in the ICP process, an electric discharge tube made of quartz is arranged between the process chamber and the vacuum pump, and is reduced gradually in thickness when it is used for a long time. Thus, in some cases, there is a possibility that the electric discharge tube becomes damaged due to the pressure of the vacuum pump. The CCP process has a drawback in that ion particles are generated in the process chamber.
Accordingly, it is an object of the present invention to eliminate the drawbacks as mentioned above by providing a plasma, dry scrubber capable of generating the plasma uniformly in the gas scrubbing application using the plasma, and of increasing the intensity of the magnetic field so that the capability of the gas decomposition is enhanced.
It is another object of the present invention to provide a plasma dry scrubber which does not get damaged due to the pressure from a vacuum pump.
To accomplish the aforementioned objects, in accordance with one aspect of the present invention, a plasma dry scrubber decomposes the introduced gas in a plasma state so that the gas is scrubbed, and comprises: a plasma generator having first and second antennas for generating the plasma; an RF generator for generating a high frequency power supply; and an impedance matching unit, connected between the first and second plasma generating antennas and the RF generator, for receiving and impedance matching the high frequency power supply signal generated by the RF generator, and then feeding the impedance matched signal to the first and second antennas.
The plasma generator includes: a housing having a gas inlet port through which gas to be scrubbed is introduced; a gas outlet port through which the scrubbed gas is discharged; a plasma generating chamber formed between the gas inlet port and the gas outlet port; first and second receiving units provided at upper and lower parts, respectively, of the plasma generator for receiving the first and second antennas, respectively; and first and second isolating plates mounted on the first and second receiving units, respectively, for isolating the first and second antennas from the plasma generating chamber.
In a preferred embodiment, the first and second isolating plates are made of ceramic or quartz. The first and second antennas have spiral configurations, and the first and second antennas are connected electrically in series with each other or electrically in parallel with each other so that magnetic fields are generated in the same or opposite directions, respectively.
In a preferred embodiment, the RF generator is a frequency-variable high frequency generator. The impedance matching unit comprises a plurality of variable capacitors.
According to the present invention, magnetic fields are generated by the first and second antennas mounted on the upper part and the lower part, respectively, of the plasma generator, and are distributed more uniformly in a plasma generating chamber so that plasma discharge is accomplished uniformly. Also, non-conductive isolating plates made of ceramic or quartz are provided for isolating the first and second antennas from the plasma generating chamber. The plates are sufficiently thick to bear up against the pressure from a vacuum pump.